In an underground exacavation, rock which has been fragmented by blasting is removed from the working area during a "mucking" operation. The rock or muck pile commonly has a steep angle of repose which can be difficult to penetrate by a bucket or other implement used for removing muck. If a loading apparatus carrying the bucket or equivalent utilizes tractive force from ground contacting means, e.g., wheels or crawler tracks, which can be termed mobile mounting means, rapid wear of the mounting means and power train producing the tractive effort results due to scuffing and heavy forces incurred.
Loading apparatus for mucking operations commonly include a conveyor assembly having a gathering device at one end, for example a bucket, a backhoe, gathering arms or a scraper, which is adapted to load material onto a fixed apron or hopper for feeding onto a lower portion of the conveyor. The gathering devices sometimes require a high degree of operator skill, usually suffer from high wear rate and low capacity and, if used with an articulated boom, require considerable head room for operation which can be inappropriate in a low head room mine. The apron of the conveyor assembly is forced into the muck pile by driving the apparatus forward, resulting in the rapid wear of the drive train as outlined above, and also in wear of gathering devices. Commonly, excessive undulations or undesirable gradients of the ground supporting the apparatus, and resilience of tires or suspension result in poor control of the plane of the resulting road bed under the muck heap. The scraper or bucket of the gathering device usually loads the conveyor in a series of discrete feeding strokes interspersed with non-productive recovery strokes, and thus material is fed intermittently onto the apron reducing potential production.
Attempts have been made to reduce the intermittent nature of feeding of material onto the conveyor by use of auxiliary or essentially continuous feeder devices designed to feed material onto the conveyor at a more constant rate than buckets, etc. Some devices use vibrating or reciprocating fingers adjacent the leading portion or apron of the conveyor to loosen material in the muck pile to facilitate entry of the apron or penetrating lip as the conveyor is advanced into muck pile. Many of these devices have an excessive number of parts which are exposed to wear when disturbing a muck pile, and it is felt that they would not be appropriate for material normally encountered in the harsh environment of mucking operations in hard rock excavation. Devices of these general types are shown in U.S. Pat. Nos. 1,855,998 (Shannon); 1,903,672 (Hauge); 1,414,398 (Dennis) and 1,878,037 (Vodoz). Other loading devices having a vibrating trough or plate adjacent the leading portion of the conveyor have been used in coal mining in combination with vibrating or shaking conveyors. The plate is mounted directly on the conveyor to shake therewith, but such devices would be inappropriate in hard rock mining, and furthermore, are limited by a very shallow angle of operation, thus requiring excessively long conveyors to attain a reasonable discharge height onto a waiting conveyance.